單片機(jī)實(shí)驗(yàn)：實(shí)驗(yàn)六 DA轉(zhuǎn)換實(shí)驗(yàn)

實(shí)驗(yàn)六D/A轉(zhuǎn)換實(shí)驗(yàn)一、實(shí)驗(yàn)?zāi)康模?．了解D/A轉(zhuǎn)換的基本原理。了解D/A轉(zhuǎn)換芯片0832的性能及編程方法。了解單片機(jī)系統(tǒng)中擴(kuò)展D/A轉(zhuǎn)換的基本方法。二、實(shí)驗(yàn)設(shè)備：EL-MUT-III型單片機(jī)實(shí)驗(yàn)箱、8051CPU模塊三、實(shí)驗(yàn)內(nèi)容：利用DAC0832，編制程序產(chǎn)生鋸齒波、三角波、正弦波。三種波形輪流顯示。四、實(shí)驗(yàn)原理：D/A轉(zhuǎn)換是把數(shù)字量轉(zhuǎn)換成模擬量的變換，從D/A輸出的是模擬電壓信號(hào)。產(chǎn)生鋸齒波和三角波只需由A存放的數(shù)字量的增減來控制；要產(chǎn)生正弦波，較簡(jiǎn)單的手段是造一張正弦數(shù)字量表。取值范圍為一個(gè)周期，采樣點(diǎn)越多，精度就越高。本實(shí)驗(yàn)中，輸入寄存器占偶地址端口，DAC寄存器占較高的奇地址端口。兩個(gè)寄存器均對(duì)數(shù)據(jù)獨(dú)立進(jìn)行鎖存。因而要把一個(gè)數(shù)據(jù)通過0832輸出，要經(jīng)兩次鎖存。典型程序段如下：MOVDPTR，#PORTMOVA，#DATAMOVX@DPTR,AINCDPTRMOVX@DPTR,A其中第二次I/O寫是一個(gè)虛擬寫過程，其目的只是產(chǎn)生一個(gè)WR信號(hào)。啟動(dòng)D/A。五、實(shí)驗(yàn)電路：六、實(shí)驗(yàn)步驟：DAC0832的片選CS0832接CS0，輸出端OUT接示波器探頭。將短路端子DS的1、2短路七、程序框圖T14.ASM主程序MAIN鋸齒波顯示子程序：PRG1三角波顯示子程序：PRG2正弦波顯示子程序：PRG3中斷子程序：DELAY;實(shí)驗(yàn)接線：DAC0832的片選CS0832接CS0，輸出端OUT接示波器探頭。NAMET92;0832數(shù)模轉(zhuǎn)換實(shí)驗(yàn)PORTEQU0CFA0HCSEGAT4000HLJMPSTARTCSEGAT4100HSTART:MOVR1,#02H;置計(jì)數(shù)初值于R1ACALLPRG1;顯示鋸齒波MOVR1,#01H;置計(jì)數(shù)初值于R1ACALLPRG2;顯示三角波MOVR1,#01H;置計(jì)數(shù)初值于R1ACALLPRG3;顯示正弦波LJMPSTART;轉(zhuǎn)START循環(huán)顯示PRG1:MOVDPTR,#PORT+1;DAC寄存器端口地址送DPTR問題1、端口地址是多少？MOVA,#00H;初值送ACCLOOP:MOVB,#0FFHLOOP1:MOVDPTR,#PORT;DAC輸入寄存器端口地址MOVX@DPTR,A;送出數(shù)據(jù)INCDPTR;問題2、加一，,是什么寄存器端口地址MOVX@DPTR,A;啟動(dòng)轉(zhuǎn)換INCA;數(shù)據(jù)加一CJNEA,#0FFH,LOOP1MOVA,#00HDJNZB,LOOP1DJNZR1,LOOP;計(jì)數(shù)值減到40H了嗎?沒有則繼續(xù)RET;產(chǎn)生鋸齒波問題3、描述鋸齒波是如何產(chǎn)生的？PRG2:MOVDPTR,#PORT+1MOVA,#00HLP0:MOVB,#0FFHLP1:MOVDPTR,#PORT;LP1循環(huán)產(chǎn)生三角波前半周期MOVX@DPTR,AINCDPTRMOVX@DPTR,AINCACJNEA,#0FFH,LP1;數(shù)據(jù)為FFH嗎?不等則轉(zhuǎn)LP1MOVR2,#0FEHLP2:MOVDPTR,#PORT;LP2循環(huán)產(chǎn)生三角波后半周期MOVA,R2MOVX@DPTR,AINCDPTRMOVX@DPTR,ADJNZR2,LP2DJNZB,LP1DJNZR1,LP0;計(jì)數(shù)值到80H則退出執(zhí)行下一步RET問題3、描述三角波是如何產(chǎn)生的？PRG3:MOVB,#00HLP3:MOVDPTR,#DATA0MOVR4,#0FFH;FFH為DATA0表中的數(shù)據(jù)個(gè)數(shù)LP4:MOVXA,@DPTR;從表中取數(shù)據(jù)MOVR3,DPHMOVR5,DPLMOVDPTR,#PORTMOVX@DPTR,AINCDPTRMOVX@DPTR,AMOVDPH,R3MOVDPL,R5INCDPTR;地址下移DJNZR4,LP4DJNZB,LP3DJNZR1,PRG3RET問題4、描述正弦波是如何產(chǎn)生的？DATA0:DB80H,83H,86H,89H,8DH,90H,93H,96H DB99H,9CH,9FH,0A2H,0A5H,0A8H,0ABH,0AEH DB0B1H,0B4H,0B7H,0BAH,0BCH,0BFH,0C2H,0C5H DB0C7H,0CAH,0CCH,0CFH,0D1H,0D4H,0D6H,0D8H DB0DAH,0DDH,0DFH,0E1H,0E3H,0E5H,0E7H,0E9H DB0EAH,0ECH,0EEH,0EFH,0F1H,0F2H,0F4H,0F5H DB0F6H,0F7H,0F8H,0F9H,0FAH,0FBH,0FCH,0FDH DB0FDH,0FEH,0FFH,0FFH,0FFH,0FFH,0FFH,0FFH DB0FFH,0FFH,0FFH,0FFH,0FFH,0FFH,0FEH,0FDH DB0FDH,0FCH,0FBH,0FAH,0F9H,0F8H,0F7H,0F6H DB0F5H,0F4H,0F2H,0F1H,0EFH,0EEH,0ECH,0EAH DB0E9H,0E7H,0E5H,0E3H,0E1H,0DEH,0DDH,0DAH DB0D8H,0D6H,0D4H,0D1H,0CFH,0CCH,0CAH,0C7H DB0C5H,0C2H,0BFH,0BCH,0BAH,0B7H,0B4H,0B1H DB0AEH,0ABH,0A8H,0A5H,0A2H,9FH,9CH,99H DB96H,93H,90H,8DH,89H,86H,83H,80H DB80H,7CH,79H,76H,72H,6FH,6CH,69H DB66H,63H,60H,5DH,5AH,57H,55H,51H DB4EH,4CH,48H,45H,43H,40H,3DH,3AH DB38H,35H,33H,30H,2EH,2BH,29H,27H DB25H,22H,20H,1EH,1CH,1AH,18H,16H DB15H,13H,11H,10H,0EH,0DH,0BH,0AH DB09H,8H,7H,6H,5H,4H,3H,2H DB02H,1H,0H,0H,0H,0H,0H,0H DB00H,0H,0H,0H,0H,0H,1H,2H DB02H,3H,4H,5H,6H,7H,8H,9H DB0AH,0BH,0DH,0EH,10H,11H,13H,15H DB16H,18H,1AH,1CH,1EH,2